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tracing: Rewrite filter logic to be simpler and faster
Al Viro reviewed the filter logic of ftrace trace events and found it to be very troubling. It creates a binary tree based on the logic operators and walks it during tracing. He sent myself and Tom Zanussi a long explanation (and formal proof) of how to do the string parsing better and end up with a program array that can be simply iterated to come up with the correct results. I took his ideas and his pseudo code and rewrote the filter logic based on them. In doing so, I was able to remove a lot of code, and have a much more condensed filter logic in the process. I wrote a very long comment describing the methadology that Al proposed in my own words. For more info on how this works, read the comment above predicate_parse(). Suggested-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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@ -1216,12 +1216,11 @@ struct ftrace_event_field {
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int is_signed;
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};
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struct prog_entry;
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struct event_filter {
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int n_preds; /* Number assigned */
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int a_preds; /* allocated */
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struct filter_pred __rcu *preds;
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struct filter_pred __rcu *root;
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char *filter_string;
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struct prog_entry __rcu *prog;
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char *filter_string;
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};
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struct event_subsystem {
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@ -1413,12 +1412,8 @@ struct filter_pred {
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unsigned short *ops;
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struct ftrace_event_field *field;
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int offset;
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int not;
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int not;
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int op;
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unsigned short index;
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unsigned short parent;
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unsigned short left;
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unsigned short right;
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};
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static inline bool is_string_field(struct ftrace_event_field *field)
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